Synthetic paper yarn



United States Patent M 3,282,038 SYNTHETIC PAPER YARN James Donald Howell, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del, a corporation of Delaware No Drawing. Filed May 2, 1962, Ser. No. 191,723 2 Claims. (Cl. 57155) This invention relates to novel yarns and fabrics. More particularly, it relates to improved twisted paper yarns and to soft, drapable fabrics therefrom.

Twisted paper yarns are well known in the art. They are generally madefrom bleached or unbleached kraft paper, which is wound into large rolls, and slit into strips ranging to 1% inches in width. The strips or ribbons are then wound onto large spools and finally twisted to convert them to yarn. The yarns, optionally impregnated with various wet strength resins or reinforced with continuous filaments or wire, find use in such applications as package strapping and tying twine. Among the other known uses for twisted paper products are automobile scat covers, fiber rugs, upholstery and luggage, chair coverings, baskets, bagging, and rug 'backings. Because of their inherent paper-like characteristics twisted paper products have been restricted to those uses where it is not essential to have the degree of softness and drape, which is normally associated with cloth. Thus, the stiffness and relative coarseness of twisted paper yarns, combined with their poor abrasion resistance, tear strength, and cleanability, make them unacceptable for use in apparel from an aesthetic as well as a practical standpoint.

It is an object of this invention to provide improved twisted paper yarns. It is a further object of this invention to provide twisted paper yarns which are eminently suitable for use in apparel. It is a still further object of this invention to provide a high bulk, high covering power, low-basis weight twisted paper yarn. It is a still further object of this invention to provide tough, twisted paper yarn fabrics of high wet strength having a unique combination of softness, limpness, and conformability.

The objects of this invention are accomplished by preparing a lightweight paper from a mixture of fibrids and synthetic fiber stable. Paper-making techniques are used to prepare a waterleaf of the fibrids and staple and the fibrids in said Waterleaf are fused in the absence of pressure to effect bonding. The resulting paper is cut into narrow strips and twisted to convert the strips into yarns. The yarns obtained are soft and bulky and can be successfully woven or knitted into fabrics by conventional methods. The fabrics obtained have a unique combination of softness, limpness and conformability.

By lightweight is meant a paper having a basis weight of less than about 1 oz./yd. preferably between about 0.2 and 0.6 oz./yd. The use of fibrids as binder permits the production of very lightweight papers having sufficient strength to be successfully processed into yarns. These papers are very thin to the point that it is possible to see through them. Their thickness can vary from as low as 1.5 mils or less for a 0.2 oz./yd. fused paper to about 5 mils or slightly greater for a 0.6 oz./yd. fused paper. In contrast, the twisted paper yarns obtained from them have a high degree of bulk and covering power.

Fibrids and their preparation are described in US. Patent No. 2,999,788 to Morgan. For the purposes of this invention the fibrids may be composed of any of the various polymers disclosed in said patent and prepared by any of the procedures mentioned therein.

The staple fibers may be derived from any wholly synthetic, polymeric material. Suitable well known polymeric materials are polyamides, such as polyhexamethylene adipamide, polyesters such as polyethylene terephthalate, and acrylonitrile polymers and copolymers. The

3,282,038 Patented Nov. 1, 1966 staple fibers may also be blended with staple fibers of other man-made polymeric materials, such as rayon or cellulose acetate, or with naturally occurring staple fibers, such as cotton. The staple fibers may vary in denier from about 0.5 to about 10 and in length from about /s to about 1 inch.

Due to the morphology of the fibrid, its drainage characteristics from aqueous suspensions (as expressed in freeness numbers), and the tenacity of waterleaves formed from liquid suspensions, such suspensions are useful for the making of sheet-like products, i.e., a synthetic paper, by paper-making techniques.

In order to obtain yarns and fabrics having the desired aesthetic properties, it is essential to start with a fibrid/ staple fiber paper, which has been fusion-bonded in the absence of pressure. If such papers are calendered, i.e., fused under pressure, the resulting yarns and fabrics are stiff and coarse. Thus, in the production of these papers, any calendering step is omitted.

The papers may be prepared using the paper-making process and machinery describe-d in the aforementioned patent to Morgan. Thus, a slurry of fibrids is fed through a beater to a stock tank where a slurry of staple fiber in the desired amount is added. The resulting fluid mass is agitated to provide uniform dispersion of solids and the amount of liquid present is adjusted. The dispersion is fed to the Fourdrinier wherein the waterleaf is laid down. The waterleaf is then pressed and dried without calendering.

Fusion-bonding is accomplished by subjecting the dried sheet to a temperature above the melting temperature of the fibrids and below the melting point of the staple fibers. Suitably, fusion-bonding is accomplished by exposing the dried sheet to a hot gas, such as air or gaseons products of combustion or by contacting the sheet with a hot surface. The equipment used must be capable of bringing the sheet up to the required temperature in a controlled and uniform manner in such a way as to allow the sheet to shrink. Two pieces of equipment which are satisfactory are the textile pin tenter frame and the National Heat-Set Machine (product of National Drying Machinery Company, Philadelphia, Pa). Optionally, fusion-bonding may be accomplished in conjunction with paper-making, immediately after passage over the drier rolls.

Fusion temperatures will, of course, be determined by the melting points of the fibrous components in the sheet structure. In general, fusion temperature is desirably at least 30 C. below the melting temperature of the polymer used in the preparation of the staple fiber component. Form any composite sheets containing polyamide, polyester, or acrylic polymer fibrids, fusion temperatures between 180 C. and 230 C. are preferred.

Fusion-bonded papers suitable for preparing the yarns and fabrics of this invention contain at least about 5% by weight of fibrids. Preferred papers comprise from about 15% to about 60% by weight of fibrids and from about to about 40% by weight of staple fibers. The paper may be described as a fused, uncalendered sheet of staple fibers bonded by physical entwinement with a plurality of fibrids. The fibrids in turn, may be defined as a plurality of supple wholly synthetic polymeric par- The yarns of this invention are made by slitting the fused papers into strips or ribbons and twisting the strips into yarns. The paper may be slit into strips ranging from about 34. inch to about 1% inches in width depending on the desired yarn denier. Different denier yarns can be obtained by varying the basis weight of the paper used and/or the width to which the paper is slit. Thus a 1 oz./yd. paper, such as described in Example I below, can be slit into inch strips and twisted into yarns having a denier of the order of 2000. By increasing the width of this strip to 1% inches, coarse yarns having a denier of about 10,000 can be obtained. Fine yarns having a denier of the order of 100 can be obtained by using 0.2 oz./yd. paper cut to inch wide strips. Conventional paper or film slitting equipment, utilizing multiple knives or rotary discs, is suitable for slitting the fused, fibrid-bonded paper.

Twisting may be done on a conventional ring downtwister, preferably equipped with a spring-loaded, rubber idler roll to provide positive feed of the paper between the idler roll and the drive roll. In addition, the strip may be passed through a forming die or trumpet prior to a 10% solution. This solution is injected at a temperature of 90 C. through a nozzle with an inside diameter of inch at a rate of approximately 100 cc./min. close to the impeller of a stirrer operating at maximum speed and placed near the bottom of a two-gallon, baffled tank containing about one gallon of water. The fibrids produced are filtered and washed with water until free of solvent and precipitant.

The fibrids obtained are blended with A1 inch, 1.5 denier polyethylene terephthalate fibers to give a 70/30 fiber/fibrid slurry. This slurry is continously deposited on an inclined wire Fourdrinier paper-making machine to produce a paper having a basis weight of 0.5 oz./yd. The paper is subjected to a fusing temperature of 220 C. for 1 minute on a textile pin tenter frame. The fused paper is then slit into inch wide strips. The untwisted strips have a denier of 986, a tenacity of 0.34 gram per denier, an elongation of 17.9% and an initial modulus of 9.3 grams per denier. The strips are then twisted on a ring downtwister into yarns having 5-20 turns per inch Z twist. The properties of the twisted yarn are given on the table below:

Properties Turns/inch Z Twist Denier Tenacity (g.p.d.) Elongation (percent). Initial Modulus (g.p.d.) 8

the point of twist to insure formation of a round y-a'rn with uniform twist and free of flat spots. The amount of twist imparted to the yarn may also be varied depending on the use for which the yarn is intended. Thus, for loosely woven, lightweight fabrics such as diffusion cloth, it is preferred to :use slightly twisted yarns, i.e., yarns having up to about 5 turns per inch twist. In such uses, the yarns of this invention provide the added advantage of high covering power fora low-basis weight fabric.

In the following examples the tensile properties of the yarns are measured on an Instron tester, using 10 inch sample lengths and elongating at 60% per minute (6 inch per minute crosshead speed). Measurements are made at 75 F. and 55% relative humidity.

Initial modulus is determined by measuring the initial slope of the stress-strain curve.

Toughness is determined by measuring the area under the stress-strain curve and then dividing this quantity by the yarn denier.

Crease recovery is measured by the Monsanto crease recovery test according to the procedure described in MATM 650902, except that the sample width is determined by using the diameter of the twisted yarn.

Wet strength is determined by TAPPI test T45 6M49.

EXAMPLE I An 80/20 ethylene terephthalate/ethylene isophthalate copolymer is added to N,N-dimethylformamide to produce The yarns obtained are soft, flexible, and bulky and can be knitted or woven into fabrics on conventional equipment.

One-fourth inch wide strips of the fibrid-bonded syn- I thetic fiber paper described in Example I are twisted into yarns having 7 turns per inch Z twist and woven into a plain weave fabric having 28 ends per inch in the warp and 22 ends per inch in the fill. The woven fabric is then subjected to a mild fulling treatment. The resulting fabric has a basis weight of 8.5 oz./yd. and a thickness of 41 mils. The fabric has a tenacity of 5 1b./in./oz./yd. and 1.9 lb./i-n./oz./yd. and an elongation of 34% and 26% in the warp and fill directions, respectively. The fabric has a soft, pleasant cashmere-like hand and is suitable for use in apparel.

EXAMPLE II A fibrid/ staple fiber paper having a basis weight of 0.45 oz./yd. and containing by weight of 1.5 denier, inoh poly (hexamethyleneadiparnide) staple fiber and 35% by weight of fibrids prepared by shear precipitation as in Example I from a 20/80 copolymer of poly (hexamethyleneadipamide) and a polycaproamide is prepared on an inclined wire Fourdrinier paper-making machine. The paper is fused, slit and twisted as described in Example I. Properties of the yarn are listed in the table below:

Turns/inch Z Twist Properties 0 k 5.5 l 6.7 i 7.9 11.1 I 14.5 I 17.8 1 19.5

It is also possible to prepare low denier yarns having an increases tenacity by subjecting the twisted yarns to a hot-stretching operation. Equipment of the type commonly used for hot-stretching yarns, cords, and the like is suitable for this operation. A multi-pass hot-stretching oven of the type shown in U.S. 2,807,863 may be used. Depending on the amount of stretch desired, the temperature and other conditions of stretching may be varied in accordance with common pratice well known to those skilled in the art. The temperature should be high enough to render the yarn sufficiently plastic to be deformed.

EXAMPLE III The fibrid-bonded synthetic fiber paper described in Example 11 is out into inch wide strips and twisted into yarn having 7.4 turns per inch Z twist. The twisted yarn is then stretched in two successive single passes through a hot-stretching oven Model C-300, sold by W. M. Steele Co., Worchester, Mass. The temperatures and conditions utilized in each pass are given in the table below:

STRETCHING CONDITIONS Pass I Pass II Temperature F.) 325 350 Draw Ratio 1/1. 22 1/1.33 Yarn Speed (it./1nin.) 25 43 Stretch (percent) 21. 3 33 The percent stretch imparted to the yarn in the second pass is calculated on the yarn length after Pass I. Arfter both passes, the total stretch imparted to the yarn, based on its original length, is 62%. The resulting yarn is more compact than the original yarn and is similar in appearance to a worsted system yarn. Its denier is reduced by about one half, while its tenacity is nearly doubled. Properties of the yarn before and after the stretching are shown in the following table:

YARN PROPERTIES Unstretehed Pass I Pass II Denier 910 657 485 Tenacity (g.p.d.) 0. 58 0. 84 0.95 Elongation (percent). 22.7 9.6 14.6 Initial Modulus (g.p.d.) 3.3 14.8 15. 2

Fabrics having a cashmere-like hand can be produced firom the yarns of this invention. In addition, these fabrics have a unique combination of softness, limpness, and conformability hitherto unattainable from spun or continuous filament yarns, as well as known paper yarns.

It is also possible to prepare fabrics from blends of these yarns and, for example wool yarns. Such fabrics are soft and resilient and eminently suitable for use in outer apparel, such as suits, sport coats, and the'like.

The fabrics of this invention may be subjected to various chemical or mechanical finishing treatments to modify their hand, drape, or appearance. For example, the loft of these fabrics may be further increased by subjecting them to a felting or fulling operation. The fabrics may be subjected to dyeing, napping, shearing, semidecating, calendering, embossing, or other finishing opera tions. They may be coated or laminated to other substrates.

The fabrics, yarns, and/ or the starting materials may be modified by incorporating various additives, such as dyes, fillers, sizes, plasticizers, etc. In some cases it may be desirable to incorporate the additives in the fibrids. This may be accomplished by adding the agent to the polymer solution prior to fibrid formation.

Twisted paper yarns prepared from fused, fibrid-bonded papers are softer and more bulky than known paper yarns. By reason of their aesthetic properties they can be converted into fabrics, which more nearly resemble cloth than paper. In comparison with conventional kraft twisted paper yarn, the yarns of this invention are capable of elongating to a greater extent before b-realeing and have a significantly lower initial modulus. It is believed that these properties are indicative of the softness and flexibility of the yarns. In addition to their highly valuable aesthetic properties, the yarns of this invention, are tougher, more resilient, and have a greater wet strength than conventional paper yarns. These properties are important for apparel uses w here' durability and washability are vital considerations. In the table below, the properties of yarns prepared from a paper containing by weight of 1.5 d.p.f., 4 inch polyethylene terephthalate staple fibers and 20% by weight of fibrids prepared from an 80/20 ethylene terephthalate/ethylene isophthalate copolyester are compared with those of a commercially available kraft paper yarn which has been treated with a melamine-formaldehyde resin to provide improved wet strength.

Fibrid-Bonded Kraft Paper Paper Basis Weight (on/yd!) 1 1 0.75 Strip Width (in.) 34 Twist (turns/in.) 6. 7 7.8 3. 5 Denier 2, 143 4, 700 3, 212 Tenacity (g.p.d. 0.790 0. 784 0.952 Toughness (gm. 0.140 0.195 0.016 Elongation (percent) 25. 5 41. 8 2. 5 Modulus (g.p.d.)- 13. 8 7. 5 40. 8 Crease Recovery (percent) 47 61 16 Wet Strength (percent). 90 60 accessories such as handbags, hats and shoes; package strapping and tying twine; electrical insulation and cable filler cords; bagging and luggage.

What is claimed is:

1. A synthetic paper yarn comprising a twisted strip of a fused, uncalendered sheet of staple fibers having a denier within the range of from 0.5 to about 10 and a length from about /8 to about one inch that are bonded by physical entwinement with a plurality of supple wholly synthetic polymeric particles having one dimension of minor magnitude relative to their largest dimension, a V

large surface area and a fiber coarseness denier no greater than about 15, the said particles being further characterized by an ability to form a waterleaf having a couched wet tenacity of at least about 0.034 lb./in./-oZ./yd. when a pulp of the said particles is deposited firom a liquid suspension upon a foraminous surface, which waterleaf, when dried at a temperature below about 50 C., has a dry tenacity at least equal to its couched wet tenacity, said twisted strip having beween about 5 and 25 twists per inch and said strip before twisting have a width of between 7 about A to 1% inches and a basis weight of less than about one ounoe per square yard. 2. A woven fabric containing the yarn of claim 1.

References Cited by the Examiner UNITED STATES PATENTS 8 Brockman et a1. 57165 Kitchen 57165 Schwartz 57155 X Morgan 162-146 FRANK J. COHEN, Primary Examiner.

MERVIN STEIN, RUSSELL C. MADER, H. G. GAR- NER, J. PETRAKES, Assistant Examiners. 

1. A SYNTHETIC PAPER YARN COMPRISING A TWISTED STRIP OF A FUSED, UNCALENDERED SHEET OF STAPLE FIBERS HAVING A DENIER WITHIN THE RANGE OF FROM 0.5 TO ABOUT 10 AND LENGTH FROM ABOUT 1/8 TO ABOUT ONE INCH THAT ARE BONDED PHYSICAL ENTWINEMENT WITH A PLURALITY OF SUPPLE WHOLLY SYNTHETIC POLYMERIC PARTICLES HAVING ONE DIMENSION OF MINOR MAGNITUDE RELATIVE TO THEIR LARGEST DIMENSION, A LARGE SURFACE AREA AND A FIBER COARSENESS DENIER NO GREATER THAN ABOUT 15, THE SAID PARTICLES BEING FURTHER CHARACTERIZED BY AN ABILITY TO FORM A WATERLEAF HAVING A COUCHED WET TENACITY OF AT LAST ABOUT 0.034 LB./IN./OZ./YD2 WHEN A PULP OF THE SAID PARTICLES IS DEPOSITED FROM A LIQUID SUSPENSION UPON A FORAMINOUS SURFACE, WHICH WATERLEAF, WHEN DRIED AT A TEMPERATURE BELOW ABOUT 50* C., HAS A DRY TENACITY AT LAST EQUAL TO ITS COUCHED WET TENACITY, SAID TWISTES STRIP HAVING BETWEEN ABOUT 5 AND 25 TWISTS PER INCH AND SAID STRIP BEFORE TWISTING HAVING A WIDTH OF BETWEEN ABOYT 1/16 TO 1 1/4 INCHES AND A BASIS WEIGHT OF LESS THAN ABOUT ONE OUNCE PER SQUARE YARD. 